The instant application is related to an engine having a variable bypass turbine fan which varies the bypass ratio of the engine.
Turbine engines with high bypass ratios have good propulsive efficiency for long range cruise or loiter, but the front area can create significant drag if high speed flight is required. Low bypass turbine engines have high specific thrust, but poor fuel economy.
There is needed an engine which has the ability to vary the bypass ratio so as to improve the ability to dash at high speeds while retaining good cruise/loiter performance.